Is an RDA enough?

RDA stands for Recommended Daily Allowance.

It can also be referred to as RNI (Reference Nutrient Intake).

There’s a common misconception that RDA’s are the perfect amount you need to achieve optimum wellbeing.

However, surprisingly, this is not what there were designed for.

RDA’s began to be set during the First World War, when food rationing came in to play.

They were a MINIMUM guidance on nutrient levels to prevent people from becoming clinically diseased.

I’m not talking a little bit unwell; like a cold or a cough, I’m talking sick enough to have a measured and noticeable decline in health that may even lead to death.

To demonstrate the simplest example….

Vitamin C deficiency.

The RDA for vitamin C is set at a daily amount of 40mg.

This is roughly equivalent to an orange or a portion of cauliflower.

The RDA for vitamin C was set at this level as is was observed that any less resulted in Scurvy.

Scurvy is known as a disease of the Navy, because it was commonly seen in sea men on long voyages.

It’s estimated that around one million sailors died at sea between 1600 and 1800, when a simple cure of an orange a day could have kept them alive.

Symptoms of scurvy include muscle pain and weakness, gum disease, poor wound healing. Death occurs because bleeding can’t easily be stopped.

After this discovery, lemons became essential cargo on every voyage.

Vitamin D deficiency is also another good example.

The RDA for vitamin D is 600IU a day.

This is roughly the equivalent to 1tsp of cod liver oil. Not many other foods are high in vitamin D. Vitamin D is in fact a hormone (more on that here).

It was observed that Cod liver oil prevented Rickets – a common bone disorder seen in toddlers and children that results in slow growth, weak muscles, and bowlegs (also known as knock knees).

A long-standing tradition held that fresh air and sunshine were also good for the prevention of Rickets.

But it wasn’t until 1928, after many scientific experiments, that the reason was confirmed – the skin synthesises vitamin D when exposed to sunshine! Vitamin D helps the body absorb calcium and phosphorus for strong bones.

How much sunshine is needed exactly is individual to the person. Factors to consider include – age, skin colour, lifestyle (indoors / outdoors), clothing and most importantly, how much sunlight is available which is dependent on the hemisphere you live in.

Other RDAs

There are many other nutrient RDA levels that are similarly set to prevent certain diseases.

For example, 1.5mcg of vitamin B12 is set to prevent pernicious anaemia (tiredness, headaches, nausea, weight loss). 1mg of vitamin B1 prevents Beriberi, a condition that produces wasting of the peripheral nerves. 17mg of B3 is set to prevent Pellegra, symptoms of which include dementia.

However, what hasn’t been taken into consideration is that these levels prevent clinical deficiency instead of

……..targeting OPTIMUM HEALTH!

So, for some nutrients, actual peak requirements are likely to be much more.

Furthermore, we already know that there are many occasions in life when you’ll need much higher levels than even before….

When do you need more than the RDA?

These include but are not limited to….

If you’re a fussy eater, on a restricted diet, don’t often cook or prepare your own food from scratch, consume high amounts of caffeine, sugar and refined carbohydrates, have allergies/intolerances or an eating disorder.

If you smoke, take drugs or drink too much alcohol.

If you exercise a lot, do manual labour, do shift work, or work /live on a busy road or in a polluted area.

If you’re a toddler or child going through a growth spurt, a developmental leap or through puberty.

If you’re pregnant, breastfeeding or running around after multiple children.

If you’re constantly stressed or depressed, working or studying excessively hard.

If you have a digestive condition, such as Crohn’s, ulcerative colitis or coeliac that inhibits nutrient absorption.

If you’re over 50, as you absorb less from food and need more vitamins to counteract the aging processes.

If you’re unwell, for example – acutely – fighting a virus (like flu or covid-19).

Or chronically – coping with something more sinister e.g. autoimmune condition or cancer– then certain vitamin (those essential to the workings of the immune system) requirements soar (more on that here).

In fact, nutrient levels are unique to the person, because we all have different genetics and individual circumstances. Not only that, but as you’ll see from above, your individual requirements change throughout your lifetime.

Why do some nutrients have no set RDA?

Simply for comparison, some RDAs have never been set for lots of nutrients that are acknowledged as particularly important for general health and protecting against degenerative disease.

For example, there are no RDA’s for Omega 3 fatty acids, although general guidelines state 2-3 portions of oily fish a week. Yet science has proved that these fats are essential for brain, heart and joint health.

There are no RDA’s set for various antioxidants, such as flavonoids, polyphenols and carotenoids, even though we know that they give us protection from degenerative diseases like arthritis, heart disease and cancer.

Soils are depleted

Not only that, but there’s some evidence that through modern farming methods our soils are being dramatically depleted of key nutrients such as zinc and selenium which are essential to our overall health, in particular our immune systems.

Add on importation and transportation.

Now consider that many fruits and vegetables are picked too early to be transported via plane, lorry or train to then sit on the supermarket shelf for 10 days or more – meaning that an orange may have lost most of its vitamin C content but the time you eat it.

This is all important stuff to think of as we try to resume normal functioning lives in the middle of a pandemic.

We assume we know it all

The dangerous mistake we humans make time and time again, is that we assume we know it all.

But there are probably many other compounds (phytonutrients) in food that are completely essential but have not yet been discovered. Which is why vitamin pills cannot and should not be completely relied upon for optimum health.

But all things considered, you could also argue that a healthy diet (depending on what you think this is and whether you’re living the GOOD LIFE) can also not be relied upon for optimum health!

We NEED TO EAT a wide variety of fresh, unprocessed, seasonal and local foods in their natural unadulterated state throughout our entire life to maintain good health.

We also need to recognise that our requirements change with our age and circumstances, adapt accordingly, and top up on vitamin and mineral supplements when necessary.

This is of course in addition to appropriate levels of exercise and methods to maintain emotional wellbeing.

It’s a tall order and we get very little guidance.

Government recommendations

The original Government recommendation of 5 portions of fruit and vegetables a day has now been increased to 7-a day.

But it is believed that nearer 10 a day is more likely to be the optimum amount to minimise chances of developing the biggest diseases that affect the Western World.


Even 7 a day reduces your risk of these by 42%!

Plus, if you’re aiming to eat over 7 – there’s probably not going to be much room for junk in your life. (Tips on how to do this here)

Interestingly, surveys consistently show that the majority of people have below even the RDA of vitamin D, magnesium, zinc and B vitamins.

All of which are vital nutrients for health, the functioning of the immune system and fighting viral infections! Like seasonal flu and Covid-19!

More research needs to be done

Nutritional Science is in its infancy. It’s clear that more research needs to be done with the aim to reveal true levels of nutrients needed for optimum health and wellbeing.

But who is going to do this research?

Sadly, there’s a disproportionate amount of research undertaken on nutrition compared with pharmaceutical drugs. This is simply because drugs are a patentable substance that can make companies rich. Whist vitamins are cheap, natural and anyone can manufacture them.

In my opinion this is short sighted.

It’s my belief that if we invested more in research on a nutrition, then taught our findings in schools, our children may grow up healthier and require less drug treatment. In turn this could help relieve the burden on struggling NHS resources in the future.

Another opinion…

If we couple this with research looking into genetic susceptibility of certain diseases (like the kind my husband Dr Alex is currently undertaking – alongside his Covid-19 research), then we could create individualised preventative strategies and see a nation of healthy people rather than many chronically ill and suffering.

Health in Synergy at its BEST!

This is my opinion. IT makes sense to me.

What do you think the answer is to improving the health of the nation?


  1. On the flip side, what are the dangers of taking too much, for example vitamin A excess can cause osteoporosis. Do u think taking 100% rda vitamin A in a pill is safe if we already get 100% in our diet? I guess we need RDA, UL and optimum limits, ideally guided by genetics and body weight. Im making a supplement, would be good to speak to you soon 🙂

    Liked by 1 person

    • Absolutely! Vitamin A is definitely a good example of when you can have too much of a vitamin. I think 100% RDA of Vit A in a pill is unnecessary, would beta carotene be safer? I guess it’s clear, as you say, that more research needs to be done. Body weight is certainly a factor too yes! The supplement making sounds interesting, I’d love to hear more.

      Liked by 1 person

  2. Great tips! Although it makes total sense that needs and times change, I have never questioned RDA’s! Thank you. Can’t wait for the hummus recipe!!

    Liked by 1 person

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